CN113189668B - Ore searching method for sandstone-type uranium ore in basin - Google Patents
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Abstract
The invention belongs to the technical field of uranium ore exploration. Aiming at the problem that the existing method for exploring uranium ores at the basin edge is difficult to be used in the basin with higher exploration difficulty, the invention provides an ore searching method for sandstone-type uranium ores in the basin. On the basis of testing the physical properties of the rocks in the basin, processing and constraint inversion are carried out on regional weight and magnetic data to obtain the buried depth, lithology, fracture distribution and the like of the basin foundation, and the weights are configured according to the priorities of 5 factors such as the gradient of the internal uplift of the basin, the area of the uplift region, the lithology and fracture of the foundation rocks, the loss rate of uranium in the foundation rocks and the like, and the interior of the basin is preferably used for facilitating exploration of the area; on the basis, drilling is carried out on the positions of large and medium-sized fractures and development of the ore-containing target layer in the preferable favorable exploration area, 8 factors such as a mud-sand ratio, a sedimentary facies, formation development, reduction capacity of gray sandstone and the like of the ore-containing target layer are calculated/analyzed, and priority weights are configured, so that the mineralization potential evaluation of the favorable exploration area is completed.
Description
Technical Field
The invention belongs to the technical field of uranium ore exploration, and particularly relates to an ore searching method for sandstone-type uranium ores in basins.
Background
The resource amount of sandstone-type uranium ores occupies the first place of four major uranium ore types in China. Such uranium deposits are found mostly on slopes at the basin edge or in the valley of an ancient river. The basin edge has long been a major area of interest for sandstone-type uranium ore exploration. However, as such uranium mine exploration continues to develop, it has been difficult for most basin boundaries to delineate new favorable exploration areas. The raised area inside the basin is a new area for future exploration of such uranium ores. Different from the edge of the basin, the basement uplift area in the basin is covered by sedimentary strata, so that ore control factors such as uranium sources, hydrodynamic force and structures are difficult to effectively judge, and the optimization of the sandstone-type uranium deposit beneficial exploration area in the basin and the effective implementation of exploration are severely restricted.
In the past, uranium mines are explored at the edge of a basin mainly by arranging a large number of drill holes and combining a small number of other detection methods, and the exploration method is single and has higher exploration cost. Compared with the basin edge, the control factors of the internal uplift of the basin are more various, the uranium ore exploration difficulty is higher, and the method for exploring the uranium ore at the basin edge is insufficient. An effective ore finding method is required to be explored according to the characteristics of uranium ore formation control by raising in the basin.
Disclosure of Invention
Aiming at the problem that the existing method for exploring uranium mine at basin edge is difficult to be used in basin with higher exploration difficulty, the invention provides an ore exploration method for sandstone-type uranium mine in basin, which is characterized in that on the basis of testing the physical properties of rocks in basin, the processing and constraint inversion are carried out on region weight and magnetic data to obtain the buried depth, lithology, fracture distribution and the like of basin basement, the favorable exploration area is preferably selected according to the priority configuration weight of 5 factors such as the slope of uplift in basin, the area of uplift area, the lithology and fracture of basement rocks, the loss rate of basement rock uranium and the like on the basis of the criterion of 'uplift in large granite + uplift wing is large', and the favorable exploration area is preferably selected; on the basis, drilling is carried out on the positions of large and medium-sized fractures and development of the mineral-containing target layer in the optimized favorable exploration area, the cores are obtained, geological logging is carried out, geophysical logging and geological interpretation work are carried out, 8 factors such as mud-sand ratio, sedimentary facies, stratum development, reduction capacity of gray sandstone and the like of the mineral-containing target layer are calculated/analyzed, priority weights are configured, and further the mining potential evaluation of the favorable exploration area is completed.
The invention is realized by the following specific technical scheme:
an ore searching method for sandstone-type uranium ores in a basin comprises the following steps:
1. rock property measurement
Determining the main rock composition types of the basin foundation, and preliminarily delineating the spatial distribution condition of rocks with different lithological properties in the sedimentary basin and the outcrop position of the rocks; drilling a fresh rock sample at the rock outcrop, and performing density measurement and magnetic measurement; respectively carrying out statistics and Q-type clustering analysis on the measured rock density and magnetic data to clarify the density and magnetic parameters of rock samples of the same lithology and differences of the rock samples in different spatial positions;
2-fold magnetic field data processing and interpretation
2.1, downloading regional gravity and magnetic data, performing bit field separation processing on the gravity and magnetic data by using geophysical prospecting data processing and interpreting software RGIS to obtain regional gravity abnormal data, local gravity abnormal data, regional magnetic force abnormal data and local magnetic force abnormal data, converting the regional gravity abnormal data, the local gravity abnormal data and the local magnetic force abnormal data into a basic plane map, and performing comparative analysis on the measured density and magnetism of different types of rocks and the obtained basic plane map to identify the lithology of the basement rock;
2.2, inverting the fluctuation form and the burial depth of the basin foundation by using the gravity field data;
2.3 dividing the fracture based on the gravity magnetic data chart, regarding the fracture with the length of more than 300km as a deep fracture, regarding the fracture with the length of 300-50km as a medium fracture, and regarding the fracture less than 50km as a local fracture;
3. advantageous exploratory area optimization inside basin
3.1 determining a target layer containing ores;
3.2 calculating the slope of the internal ridge of the basin
Reading the peak h of the inner bulge of the basin according to the basin basement undulation form and burial depth result obtained by gravity data inversion1(ii) a According to the seismic data of the area near the bump, the buried depth h of the top of the ore-bearing target layer is read2Calculating the height difference between the two as delta h, reading the distance between the two as l, and further determining the gradient: i ═ Δ h/l) × 100%; the favorable mineralization priority and the corresponding gradient range are as follows: a is1＝5％≤i＜10％；b1I is more than or equal to 3% and less than 5% or i is more than or equal to 10% and less than 15%; c. C1I is more than or equal to 1% and less than 3% or i is more than or equal to 15% and less than 25%; d1I is more than or equal to 25 percent or more than or equal to 0 and less than 1 percent;
3.3 fracture
The area with deep and large development and more than 3 medium-sized and local fractures is defined as a2Grade, only 3 or more middle-sized, local fracture areas are defined as b2A stage; the area in which only 3 or less medium-sized, local fractures had developed was designated as c2Grade, the area of non-fragmentation development is designated as d2A stage;
3.4 type of raised area rock inside the basin
According to the priority of uranium supply of rocks of different lithologies, granite a3Grade > volcanic rock b3Grade > bedrock c3Grade > metamorphic rock d3Stage (2);
3.5 area of raised area inside basin
Dividing the uranium supply priority of the bump area into a4Stage b4Stage c4Stage d and4the minimum value of the corresponding area is i ≥ 10 × 103km2、10×103km2＞i≥5×103km2、5×103km2＞i≥1×103km2、0.5×103km2＞i；
3.6 calculation of uranium loss rate of rock sample
Collecting weathered rock samples at a defined outcrop, measuring the composition of U-Pb isotopes by using a thermal ionization mass spectrometer, calculating the loss rate delta U of uranium according to the content of the Pb isotopes, and dividing the priority of favorable uranium mineralization into a5Stage b5Stage c5Stage d and5grade, which respectively corresponds to the conditions that delta U is more than or equal to 70 percent, 70 percent is more than or equal to delta U is more than or equal to 50 percent, 50 percent is more than or equal to delta U is more than or equal to 30 percent and delta U is less than 30 percent;
3.7 favorable exploration area optimization
Weights are configured for different priorities of 5 factors of gradient of the uplift inside the basin, uplift area, lithology of basement rock, fracture and loss rate of uranium, wherein a is 5, b is 4, c is 3 and d is 2; coefficient of evaluation
XiRepresenting the weight corresponding to the priority of each factor, and primarily screening favorable exploration areas in the basin according to the result:
m is more than 4 and less than or equal to 5, and the ore-forming potential evaluation is preferentially carried out;
m is more than 3 and less than or equal to 4, and the evaluation of the ore potential can be developed;
m is more than 2 and less than or equal to 3, and the mineralization potential evaluation is not required to be carried out;
4. beneficial to the evaluation of the mineralization potential of an exploration area
4.1 carrying out drilling of boreholes
Drilling at the position favorable for development of large and medium-sized fractures and ore-bearing target layers in the exploration area in the preferable basin, obtaining a core and performing geological logging, and simultaneously performing geophysical logging and geological interpretation work;
4.2 lithology and lithofacies characteristics of the ore-bearing target layer
(1) Calculation of the mud-sand ratio
Identifying mudstone and sandstone and measuring the thickness of the mudstone and the sandstone when geological logging is carried out on a drill core, and calculating a mudsand ratio, wherein the range of the mining priority and the corresponding mudsand ratio i is favorable as follows: a is1＝0.5≤i＜0.7；b1I is more than or equal to 0.7 and less than 1.0 or i is more than or equal to 0.3 and less than 0.5; c. C1I is more than or equal to 0.2 and less than 0.3 or i is more than or equal to 1.0 and less than 1.3; d1I is more than or equal to 1.3 or more than or equal to 0 and less than 0.1;
(2) calculation of oxidized sandstone to reduced sandstone ratio
When geological logging is carried out on a drill core, yellow oxidized sandstone and gray reduced sandstone are identified, the thicknesses of the yellow oxidized sandstone and the gray reduced sandstone are measured, and the ratio I of the yellow oxidized sandstone and the gray reduced sandstone is calculated, so that the ratio range of the synthesized ore priority and the corresponding oxidized sandstone and reduced sandstone is as follows: a is2＝2.0＜i＜4.0；b2I is more than or equal to 4.0 and less than 5.0 or i is more than 1.0 and less than or equal to 2.0; c. C2I is more than or equal to 5.0 and less than 6.0 or i is more than 0.5 and less than or equal to 1.0; d2I is 6.0-0 or i-0.5;
(3) sedimentary phase partitioning
The priority of each sedimentary phase favorable for uranium mineralization is as follows: braided river delta phase a3Delta phase of stage and fan3Grade and plait river phase c3Grade and meandering stream phase d3Stage (2);
4.3 Gamma Log Curve analysis
Determining the favorable ore-formation priority and the multiple of the corresponding abnormal value thereof larger than the background according to the gamma well logging curve and the value in the ore-containing target layer as follows: a is4＝7＜i；b4＝5＜i≤7；c4＝3＜i≤5；d4＝3≤i；
4.4 evaluation of reducing ability of Gray sandstone
The relative content of the organic carbon in the gray sandstone sample is measured, so that the method is favorable for the mineralization priority and the corresponding relative content range of the organic carbon: a is5＝i≥10‰；b5＝5‰≤i＜10‰；c5＝0.5‰≤i＜5‰；d5＝i≤0.5‰；
4.5 calculation of Th/U element content ratio
The Th/U ratio of the sandstone sample containing the ore target layer is measured, and in yellow oxidized sandstone, the ratio is favorable for the mineralization priority and the corresponding range of the Th/U ratio i: a is a6＝10≤i；b6＝8≤i＜10；c6＝6≤i＜8；d6I is more than or equal to 4.5 and less than 6; in grey sandstone, the mineralization priority and the corresponding Th/U ratio i range: a is7＝i≤1；b7＝1＜i≤2；c7＝2＜i≤3；d7＝3＜i≤4.5；
4.6 analysis of spatial distribution rule of ore-bearing target layer and adjacent layer
Performing secondary analysis on the seismic data of the uplifted region in the target basin and the region near the uplifted region to know the development condition of the uplifted wing stratum in the basin, and determining that the overburden stratum has no overburden phenomenon and is degraded as a8A stage; defining the overburden-free stratum as b8A stage; the occurrence of local overburden in the overburden is determined as c8A stage; the phenomenon of large-area overburden of overburden stratum is defined as d8A stage;
4.7 evaluation of Ore-forming potential in favorable exploration area
Configuring weights for different priorities of 8 factors of mud sand ratio of an ore-bearing target layer, oxidized sandstone/reduced sandstone ratio, sedimentary facies, gamma well logging curve in the ore-bearing target layer, reduction capability of gray sandstone, Th/U element content ratio and spatial distribution of the ore-bearing target layer, wherein a is 5,b is 4, c is 3, d is 2; coefficient of evaluation
XiRepresenting the weight corresponding to the priority of each factor, evaluating the mineralization potential of the favorable exploration area in the basin according to the result,
m is more than 4.5 and less than or equal to 5, and the method has the potential of developing large sandstone-type uranium deposit;
m is more than 3.5 and less than or equal to 4.5, and the uranium ore has the potential of developing medium sandstone-type uranium ore deposits;
m is more than 2.5 and less than or equal to 3.5, and the method has the potential of developing small sandstone-type uranium deposit;
m is more than 2 and less than or equal to 2.5, and the potential of developing sandstone-type uranium ores is not realized.
Further, in the step 1, 15 outcrops need to be found for each type of lithologic rock, and each outcrop collects 3-5 rock samples; the mass of the collected rock samples needs to be more than 3kg, each rock sample is cut into 2 parts in the step 1, one part is used for density measurement, and the other part is used for magnetic measurement.
Further, carrying out rock density measurement by adopting a wax sealing method; collected bedrock and sedimentary rock samples were made into cubic test specimens, which were placed in an MS2 susceptibility meter to measure the susceptibility of the rock.
Further, in step 2, the downloading data range of the regional gravity and magnetic data is at least 3/2, preferably 2 to 3/2, of the target basin range.
Further, the step 2.2 of inverting the undulation form and the burial depth of the basin foundation by using the gravity field data comprises:
(1) on the premise of rock densities of different lithology types, separating gravity abnormal field data from gravity field data by using a wavelet analysis method;
(2) utilizing a density interface inversion module of geophysical prospecting data processing interpretation software RGIS to invert the gravity abnormal field data and preliminarily obtain the fluctuation form and the burial depth of a substrate interface;
(3) correcting the obtained basin foundation burial depth result;
(4) obtaining more accurate substrate interface fluctuation form, quantitatively calculating substrate burial depth, delineating the substrate bulge in the basin and determining the buried depth of the bulge.
Further, the step 2.3 of dividing the fracture based on the gravity and magnetic data comprises:
(1) calculating the normalized total horizontal derivative vertical derivative of the regional gravity data, forming a graph, and preliminarily dividing possible fractures according to the maximum connecting line and the staggered section of the maximum connecting line;
(2) and further determining the fracture by using the polarized magnetic force abnormal vertical first derivative of the regional gravity data and the distribution of positive and negative values of the vertical first derivative.
(3) And (3) finally determining the fracture by combining the gravity-magnetic basic plane drawing generated by 2.1 according to the abnormal dislocation obtained after the data processing in the step (2).
Further, for sedimentary basins for which a mineralised destination layer has not been determined, the mineralised destination layer may be determined from step 3.1 because the history of structural evolution experienced by adjacent sedimentary basins is substantially the same, substantially consistent with mineralised destination layers for nearby sedimentary basins.
Further, the step 3.2 of calculating the slope of the ridge inside the basin comprises the following steps: determining the top burial depth of the ore-bearing target layer in the seismic section near the inner bulge of the delineated basin; reading the peak h of the inner bulge of the basin according to the basin basement undulation form and burial depth result obtained by gravity data inversion1(ii) a According to the seismic data of the area near the bump, the buried depth h of the top of the ore-bearing target layer is read2. Calculating the height difference between the two as delta h-h1–h2And the distance between the two is read as l, and the gradient i is (Δ h/l) × 100%.
Further, in step 3.5, the calculation method of the area of the raised area inside the basin includes: according to the seismic data, identifying the top boundary of the ore-bearing target layer near the raised area in the basin, and approximating the top boundary to the bottom of a conical body with radius r2The generatrix is l2Surface area of the cone: s1＝πr2l2(ii) a The top of the raised area in the basin is approximately round with the radius r1Area: s3＝πr1 2(ii) a Top of raised area in basinRadius of the above cone is r1The generatrix is l1Surface area: s2＝πr1l1(ii) a Surface area of raised area inside basin: s ═ S1–S2+S3＝πr2l2–πr1l1+πr1 2。
Further, the step 3.6 of calculating the uranium loss rate of the rock sample comprises the following steps: at the outcrop collection rock sample of circle definite weather, utilize thermal ionization mass spectrograph to carry out the survey of U-Pb isotope composition to it, calculate original uranium content through Pb isotope content, judge the condition of losing of uranium with present uranium content comparison again, the computational formula is: uranium loss rate Δ U ═ U/U0-1) × 100%, where U is the present uranium content of the sample, U0Original uranium content of the sample.
The ore searching method for the sandstone-type uranium ores in the basin aims at key ore control factors of the raised base of the basin and the sedimentary strata near the raised base of the basin, truly performs accurate optimization of favorable exploration areas in the basin and development of evaluation of ore forming potential, can effectively improve exploration efficiency and shorten exploration period. In addition, the publicly downloaded gravity and magnetic data and literature data are fully utilized, and the exploration cost is greatly saved.
Drawings
FIG. 1 is a uranium mineralization pattern of an interior uplift region of an embodiment basin;
FIG. 2 is a schematic diagram of a calculation of the surface area of the raised area inside the basin according to the embodiment;
fig. 3 is a flow chart of an ore prospecting method for sandstone-type uranium ore in a basin.
Detailed Description
The present invention will be described in further detail with reference to the following embodiments and the accompanying drawings.
Examples
An ore exploration technical method for sandstone-type uranium ores in basins specifically comprises the following steps:
1. rock physical property (density, magnetism) measurement
1.1 consulting the data, determining the main rock composition types of the basin foundation, preliminarily delineating the spatial distribution conditions of rocks (granite, bedrock, metamorphic rock and the like) with different lithologies in the sedimentary basin, and determining the outcrop position of the rocks so as to collect samples.
1.2 carry out the open-air geological survey and sample work
(1) And searching corresponding rock outcrops according to the determined positions of the rock outcrops exposing to the earth surface from the basement rocks and the sedimentary rocks with different lithologies.
(2) A fresh rock sample was drilled out of the rock with a core sampler. And (3) finding 15 outcrops for each type of lithologic rock, and collecting 3-5 rock samples for later-period data statistics and analysis by each outcrop. The mass of the collected rock sample needs to be more than 3 kg. Each rock sample was cut into 2 parts, one for density measurement and the other for magnetic measurement.
1.3 adopt the wax sealing method to carry out the rock density measurement, the concrete operation step:
(1) selecting approximately cubic rock with the side length of 5cm, flattening edges and corners, and brushing off surface stickers;
(2) putting the sample into a drying oven at 110 ℃ until the weight of the sample is constant, taking out the sample, putting the sample into a drying chamber, cooling the sample to a constant temperature, and weighing the sample to obtain g;
(3) the sample was bound with a thread, placed in paraffin wax just after the melting point, and taken out after 1-2 s, and the paraffin wax on the sample was examined for bubbles. If necessary, the holes can be punctured and coated by a small electric iron or a hot needle, and the weight is weighed on a balance to obtain g1；
(4) Hanging the wax-sealed sample on a balance hook, and weighing in water to obtain g2；
(5) And (3) calculating the density: dg＝g/((g1-g2)/ds)–((g1-g)/gn)
In the formula: dgDry density of the rock, unit: g/m3；
g-dry weight of sample, unit: g;
g1weight of wax-sealed sample in air, unit: g;
g2weight of wax-sealed sample in WaterAmount, unit: g;
dsdensity of water, unit: g/m3；
dsDensity of paraffin wax, unit: g/m3。
1.4 carrying out rock magnetism measurements
Making the collected bedrock and sedimentary rock samples into 1cm3The cubic sample of (2) was placed in an MS2 susceptibility meter to measure the susceptibility of the rock.
1.5 statistics and analysis of rock Density and magnetic measurements
And (3) carrying out statistics and Q-type clustering analysis on the measured rock density and magnetic data by using a statistical product and service solution software SPASS. The density and magnetic parameters of rock samples of the same lithology type and the difference of the rock samples in different spatial positions are clarified.
2. Processing and interpreting of heavy and magnetic field data
(1) And determining the range of the data to be downloaded according to the position of the target basin. To ensure the effectiveness of the target basin data effort of the post-data processing, the downloaded data scope needs to be 3/2 of the target basin scope.
(2) And downloading 1:20 ten thousand of regional gravity and magnetic data at a geological cloud website (geocoudso. cgs. gov. cn /) according to the determined range of the downloaded data.
2.1 identifying lithology of basement rock based on heavy magnetic field characteristics
In order to better identify the lithology of the basement rock, deep basement anomalies need to be highlighted, shallow sedimentary layer anomalies need to be attenuated, and the following work needs to be carried out:
(1) under the constraints of the density and magnetic parameters of rocks with different lithological properties, geophysical prospecting data processing interpretation software RGIS is used for carrying out bit field separation processing on the gravity data so as to obtain regional gravity anomaly data, local gravity anomaly data, regional magnetic force anomaly data and local magnetic force anomaly data, and forming a map.
(2) And generating a basic plane drawing by data calculated by conversion technologies such as analytic extension, horizontal first-order derivatives in different directions and the like.
(3) And comparing the measured density and magnetism of different types of rocks with the obtained basic plane graph to analyze so as to identify the lithology of the basement rock.
Criteria for identifying lithology: generally, metamorphic rocks are used for high density and weak magnetism; the density is small, and the magnetism is strong, namely granite; the high-density and strong-magnetism rock is (super) bedrock.
2.2 inversion of basin basement relief morphology and burial depth using gravitational field data
The density difference between the underlying base rock and the overlying sedimentary rock is obvious, and the method is favorable for carrying out gravity field data inversion basin base fluctuation form and burial depth.
(1) On the premise of rock densities of different lithology types, separating gravity abnormal field data from gravity field data by using a wavelet analysis method;
(2) utilizing a density interface inversion module of geophysical prospecting data processing interpretation software RGIS to invert the gravity abnormal field data and preliminarily obtain the fluctuation form and the burial depth of a substrate interface;
(3) due to the multiple solution of the obtained basin foundation burial depth result, the constraint is required to be carried out through other geological and geophysical data. The burial depth of the substrate at the location of the borehole/seismic section can be determined from borehole, seismic and geophysical log data, using these points as correction points. And comparing the base depth of the correction point and the corresponding coordinate thereof with the basin base buried depth result obtained by inversion, and debugging codes and set parameters to enable the base buried depth inversion result to be consistent with the buried depth of the correction point position base in the drilling/seismic profile. In case of great difference from the actual situation, the reason needs to be found, and the code is debugged and the parameters are modified continuously. Generally, at least 5 correction points are selected to ensure the accurate inversion result of the substrate burial depth, and the selected correction points need to be uniformly distributed in the basin range.
(4) Through the work, the accurate substrate interface fluctuation form is obtained, the substrate burial depth is calculated quantitatively, the substrate bulge in the basin is defined, and the burial depth of the (hidden) bulge is determined.
2.3 partitioning fractures based on gravity magnetic data
The presence of a fracture disrupts the continuity of the geological volume, allowing some difference in density and magnetic properties in the transverse direction. This is the theoretical basis for dividing the fracture by using the gravity magnetic data.
(1) Calculating the normalized total horizontal derivative vertical derivative of the regional gravity data, forming a graph, and preliminarily dividing possible fractures according to the maximum connecting line and the staggered section of the maximum connecting line;
(2) and further determining the fracture by using the polarized magnetic force abnormal vertical first derivative of the regional gravity data and the distribution of positive and negative values of the vertical first derivative.
(3) And (3) finally determining the fracture by combining the gravity-magnetic basic plane drawing generated by 2.1 according to the abnormal dislocation obtained after the data processing in the step (2).
(4) The finally determined fractures are classified. Fractures with a length of more than 300km are considered as deep fractures, fractures with a length of 300-50km are considered as medium fractures, and fractures less than 50km are considered as local (small) fractures.
3. Advantageous exploratory area optimization inside basin
3.1 determination of Ore-bearing target layer
Due to the influence of different position structure differences, the mineral-containing target layer of the northern sedimentary basin in China has obvious zoning. The mineral-containing target layers of the sedimentary basins in the northwest and the northeast of China are Jurassic and chalky strata respectively, and the mineral-containing target layers of the sedimentary basins in the northwest of China can be Jurassic strata and can also be chalky strata. At present, certain uranium ore exploration work is carried out on most sedimentary basins in China, and an ore-containing target layer of the basin is determined. For some sedimentary basins for which a mineralised destination layer has not been determined, the mineralised destination layer may be determined therefrom, as the history of structural evolution experienced by adjacent sedimentary basins is substantially the same, substantially consistent with mineralised destination layers of nearby sedimentary basins.
3.2 calculation of the slope of the internal ridges of the basin
(1) Determining the top burial depth of the ore-bearing target layer in the seismic section near the inner bulge of the delineated basin;
(2) according to the undulation form and the burial depth result of the basin base obtained by the inversion of the gravity data,reading the apex h of a basin internal bulge1(ii) a According to the seismic data of the area near the bump, the buried depth h of the top of the ore-bearing target layer is read2. Calculating the height difference between the two as deltah, and reading the distance between the two as l.
Height difference: Δ h ═ h1–h2
Gradient: i ═ (. DELTA.h/l). times.100%
(3) In view of the gradient of 5% -10%, uranium is most beneficial to mineralization. The more unfavourable the uranium mineralization as the gradient increases and decreases. When the gradient is larger (more than or equal to 25 percent) or smaller (less than 1 percent), uranium is not beneficial to ore formation. The favorable mineralization priority and the corresponding gradient range are determined as follows: a is1＝5％≤i＜10％；b1I is more than or equal to 3% and less than 5% or i is more than or equal to 10% and less than 15%; c. C1I is more than or equal to 1% and less than 3% or i is more than or equal to 15% and less than 25%; d1I is more than or equal to 25 percent and less than or equal to 0 and less than 1 percent.
3.3 fracture
The development of the fracture is beneficial to the supplement-radial-discharge action of the surface-generated uranium-containing fluid; fluids favorable for uranium mineralization, such as deep thermal fluids, reducing fluids, etc., intrude upward into the mineralizing target layer by fracture. These processes promote the aggregation of uranium into ore, and fracture is one of the important evaluation indexes.
The uranium deposit areas that have been identified as being produced at the raised edges inside the basin tend to develop deep fractures and multiple localized fractures. The favorable mineralizing priority of the fracture is determined according to the following steps: the area with deep and large development and more than 3 medium-sized and local fractures is defined as a2Grade, only 3 or more middle-sized, local fracture areas are defined as b2A stage; the area in which only 3 or less medium-sized, local fractures had developed was designated as c2Stage, setting the region without fracture as d2A stage;
3.4 type of raised area rock inside the basin
The uranium source for sandstone-type uranium ores typically comes from an uplifted region in its vicinity. Rocks with different lithology types have different uranium contents, so that the uranium supply capacity is different. The average uranium content of granite is 3ppm, the average uranium content of volcanic rock is 2ppm, the average uranium content of (super) bedrock is 1ppm, and the average uranium content of metamorphic rock is 1ppmThe amount of uranium is less than 1 ppm. The rocks with different lithologies are divided into the priorities of uranium supply, namely granite (a)3Class) > volcanic rock (b)3Grade) > (super) basic rock (c)3Class) > metamorphic rock (d)3Stages).
3.5 area of raised area inside basin
Generally, the larger the area of the raised area inside the basin, the greater the total amount of uranium lost and the greater the uranium mineralization potential.
(1) Calculation of the area of a bulge inside a basin
According to the seismic data, identifying the top boundary of the ore-bearing target layer near the raised area in the basin, and approximating the top boundary to the bottom of a conical body with radius r2The generatrix is l2As shown in fig. 2, the surface area of the cone: s1＝πr2l2；
The top of the raised area in the basin is approximately round with the radius r1Surface area of upper cone: s2＝πr1l1；
The radius of the conical body above the top of the raised area in the basin is r1The generatrix is l1The top area of the raised area inside the basin: s3＝πr1 2；
Surface area of the raised area inside the basin: s ═ S1–S2+S3＝πr2l2–πr1l1+πr1 2。
(2) The total area of the uranium source area of the sandstone-type uranium ore in China at present and the corresponding uranium deposit size are taken as the basis, and the priority of uranium supply of the area of the uplifted area is divided into a4Stage b4Stage c4Stage d and4the minimum value of the corresponding area is i ≥ 10 × 103km2、10×103km2＞i≥5×103km2、5×103km2＞i≥1×103km2、0.5×103km2＞i。
3.6 calculation of uranium loss rate of rock sample
15 weathered rock samples were collected on the outcrop of the delineation and subjected to U-Pb isotopic composition determination using an ISOPROBE-T thermal ionization mass spectrometer. The original uranium content is calculated according to the Pb isotope content, and then the loss condition of uranium is judged by comparing with the current uranium content U.
Original Pb content in rock:
(206Pb/204Pb)0＝9.307+μ0[(exp(λ8t0)–exp(λ8t)] (1)
where t is the age of formation of the rock sample, λ8Is composed of238Decay constant of U, value of 1.55125X 10-10/a；μ0Is composed of238U/204Atomic ratio of Pb; t is t04430Ma was used in the calculation for the age of the earth formation.
Original uranium content of the sample:
U0＝[206Pb/204Pb–(206Pb/204Pb)0]/[exp(λ8t)-1]×(Pb×204Pb×MU)/(99.274×MPb) (2)
in the formula:206Pb/204pb is the Pb isotope ratio of the rock sample; pb is the measured Pb content in the rock sample; mPbIs the atomic weight of Pb, and has a value of 207.2;204pb is rock sample204The relative percentage of Pb; muIs the atomic weight of uranium and has a value of 238.028.
Recent loss rate of uranium in rock samples:
ΔU＝(U/U0–1)×100％ (3)
the higher the loss rate of uranium in the raised rock in the basin, the more beneficial the uranium in the low terrain nearby to form ore. Calculating the average value of the loss rate (delta U) of uranium, and dividing the priority of uranium mineralization into a5Stage b5Stage c5Stage d and5and the levels correspond to the conditions that delta U is more than or equal to 70 percent, 70 percent is more than delta U is more than or equal to 50 percent, 50 percent is more than delta U is more than or equal to 30 percent and delta U is less than 30 percent respectively.
3.7 favorable exploration area optimization
Weights are assigned to different priorities of 5 factors of gradient of the uplift inside the basin, uplift area, lithology of the basement rock, fracture and loss rate of uranium, wherein a is 5, b is 4, c is 3 and d is 2.
Coefficient of evaluation
XiAnd representing the weight corresponding to the priority of each factor, and primarily screening favorable exploration areas in the basin according to the result, wherein the favorable exploration areas are more than 3 < M.
M is more than 4 and less than or equal to 5, and the ore-forming potential evaluation is preferentially carried out;
m is more than 3 and less than or equal to 4, and the evaluation of the ore potential can be developed;
m is more than 2 and less than or equal to 3, and the mineralization potential evaluation is not required to be carried out.
4. Beneficial to the evaluation of the mineralization potential of an exploration area
4.1 conducting borehole drilling
And drilling at the position favorable for development of large and medium-sized fractures and ore-bearing target layers in the exploration area in the preferable basin, obtaining the core and performing geological logging, and simultaneously performing geophysical logging and geological interpretation work.
4.2 lithology and lithofacies characteristics of the ore-bearing target layer
And (3) performing detailed recording, observation and photographing on the drilled rock core in the field, and recording the characteristics of the rock core such as color, mineral types and content, sedimentation structure and the like in detail.
(1) Calculation of the mud-sand ratio
The ore-bearing target layer has a mud-sand-mud structure, which is more beneficial to uranium gathering and ore forming, and the mudstone and the sandstone are identified and the thickness of the mudstone and the sandstone is measured when geological logging is carried out on the drill core, and the mudsand ratio is calculated. When the ratio of the silt of the ore-bearing target layer is between 0.5 and 0.7, the uranium is most beneficial to ore formation, and the uranium can be adversely affected by high or low proportion. Therefore, the favorable mineralization priority and the corresponding range of the sludge-sand ratio can be determined as follows: a is1＝0.5≤i＜0.7；b1I is more than or equal to 0.7 and less than 1.0 or i is more than or equal to 0.3 and less than 0.5; c. C1I is more than or equal to 0.2 and less than 0.3 or i is more than or equal to 1.0 and less than 1.3; d1I is more than or equal to 1.3 or more than or equal to 0 and less than or equal to 0.1.
(2) Calculation of oxidized sandstone to reduced sandstone ratio
And when geological logging is carried out on the drill core, identifying the yellow oxidized sandstone and the gray reduced sandstone, measuring the thicknesses of the yellow oxidized sandstone and the gray reduced sandstone, and calculating the ratio of the yellow oxidized sandstone to the gray reduced sandstone. The thickness ratio of the yellow oxidized sandstone to the gray reduced sandstone is about 2, which is most beneficial to uranium mineralization, and the higher or lower proportion of the yellow oxidized sandstone to the gray reduced sandstone can have adverse effects on the uranium mineralization. Therefore, the favorable mineralizing priority and the corresponding oxidized sandstone and reduced sandstone ratio range can be determined as follows: a is2＝2.0＜i＜4.0；b2I is more than or equal to 4.0 and less than 5.0 or i is more than 1.0 and less than or equal to 2.0; c. C2I is more than or equal to 5.0 and less than 6.0 or i is more than 0.5 and less than or equal to 1.0; d2I is 6.0-0 or i-0.5.
(3) Sedimentary phase partitioning
Determining sedimentary facies of a mineral-containing target layer according to geological logging of a drill core and interpretation results of a logging curve by combining a sedimentology principle, and analyzing changes of sedimentary facies sequences and spatial distribution rules of the sedimentary facies sequences. The sandstone-type uranium ores discovered at present are mostly present in stratums of plait river delta and fan delta sedimentary phases. The priority of favorable uranium mineralization of each sedimentary phase is determined as follows: braided river delta phase a3Delta phase b of class and fan3Grade and plait river phase c3Grade and meandering stream phase d3And (4) stages.
4.3 Gamma Log Curve analysis
The gamma log may directly indicate whether uranium mineralization is present at the borehole location. And (3) carrying out quantitative analysis on the gamma logging curve, wherein the uranium mineralization can be regarded as the gamma logging curve in the ore-bearing target layer when the abnormal section is more than 2m and the abnormal value is more than 3 times of the background. Thus, the favorable mineralization priority and its corresponding anomaly value may be determined to be greater than the background by a factor of: a is a4＝7＜i；b4＝5＜i≤7；c4＝3＜i≤5；d4＝3≤i。
4.4 evaluation of reducing ability of Gray sandstone
The higher the organic carbon content in the gray sandstone, the stronger the reducing power, and the more beneficial the uranium to be mineralized. 8 gray sandstone samples are adopted, and the mass of each rock sample is more than 1 kg. And testing the relative content of organic carbon in the sample by using a high-frequency infrared carbon-sulfur instrument. Thus, a favorable mineralization priority and its corresponding organic carbon relative can be determinedThe content range is as follows: a is5＝i≥10‰；b5＝5‰≤i＜10‰；c5＝0.5‰≤i＜5‰；d5＝i≤0.5‰。
4.5 calculation of Th/U element content ratio
When the rock fragments are not subjected to uranium entrainment and leaching, the Th/U ratio is about 4.5, uranium entrainment causes the Th/U ratio to decrease, and uranium leaching causes the Th/U ratio to increase.
(1) 6 samples of the gray reduced sandstone of the ore-containing target layer are adopted, and the mass of each rock sample is more than 1 kg. And measuring the content of Th and U elements of the sample by using a MUA type laser fluorescence instrument, calculating the Th/U ratio, and then calculating the average value. In gray sandstone, the smaller the Th/U ratio is, the larger the uranium carrying amount is, and the more beneficial the uranium is to mineralize. Thus, a favorable mineralization priority and its corresponding range of Th/U ratios may be determined: a is6＝10≤i；b6＝8≤i＜10；c6＝6≤i＜8；d6＝4.5≤i＜6。
(2) 6 samples of yellow oxidized sandstone of the layer containing the ore target are adopted, and the mass of each rock sample is more than 1 kg. And measuring the content of Th and U elements of the sample by using a MUA type laser fluorescence instrument, calculating the Th/U ratio, and then calculating the average value. In the oxidized sandstone, the larger the Th/U ratio is, the larger the leaching amount of uranium is, and the more beneficial the uranium is to mineralizing. Thus, a favorable mineralization priority and its corresponding range of Th/U ratios may be determined: a is7＝i≤1；b7＝1＜i≤2；c7＝2＜i≤3；d7＝3＜i≤4.5。
4.6 analysis of spatial distribution rule of ore-bearing target layer and adjacent layer
And carrying out secondary analysis on the seismic data of the uplifting area in the target basin and the area nearby the uplifting area so as to know the development condition of the uplifting wing stratum in the basin. The existing research results show that the contact relation between the ore-bearing target layer and the overlying stratum influences uranium mineralization. Wherein, the overburden phenomenon of the overlying strata is an important factor for restricting the uranium mineralization of each basin. In addition, the ore-bearing target layer is often not integrally contacted with the overlying strata, and a denudation phenomenon exists. Accordingly, the favorable uranium mineralization priority is determined: defining the overlying stratum to have no overburden phenomenon and denudation as a8A stage; defining the overburden-free stratum as b8A stage; the occurrence of local overburden in the overburden is determined as c8A stage; the phenomenon of large-area overburden of overburden stratum is defined as d8And (4) stages.
4.7 evaluation of Ore-forming potential in favorable exploration area
And configuring weights for different priorities of 8 factors of a silt ratio of the ore-bearing target layer, an oxidized sandstone ratio, a reduced sandstone ratio, a sedimentary facies, a gamma logging curve in the ore-bearing target layer, a reduction capability of grey sandstone, a Th/U element content ratio and spatial distribution of the ore-bearing target layer, wherein a is 5, b is 4, c is 3 and d is 2.
Coefficient of evaluation
XiAnd representing the weight corresponding to the priority of each factor, and evaluating the mineralization potential of the favorable exploration area in the basin to be 3.5 < M according to the result, thereby providing guidance for further exploration.
M is more than 4.5 and less than or equal to 5, and the method has the potential of developing large sandstone-type uranium deposit;
m is more than 3.5 and less than or equal to 4.5, and the method has the potential of developing medium sandstone-type uranium deposit;
m is more than 2.5 and less than or equal to 3.5, and the method has the potential of developing small sandstone-type uranium deposit;
m is more than 2 and less than or equal to 2.5, and the potential of developing sandstone-type uranium ores is not realized.
The above-mentioned embodiments are merely illustrative of the preferred embodiments of the present invention, and do not limit the scope of the present invention, and various modifications and improvements of the technical solution of the present invention by those skilled in the art should fall within the protection scope defined by the claims of the present invention without departing from the spirit of the present invention.
Claims (10)
1. An ore searching method for sandstone-type uranium ores in basins is characterized by comprising the following steps:
step 1. measurement of rock Properties
Determining the main rock composition types of the basin foundation, preliminarily delineating the spatial distribution condition of rocks with different lithological properties in the sedimentary basin and the outcrop position of the rocks; drilling a fresh rock sample at the rock outcrop, and performing density measurement and magnetic measurement; respectively carrying out statistics and Q-type clustering analysis on the measured rock density and magnetic data to clarify the density and magnetic parameters of rock samples of the same lithology and differences of the rock samples in different spatial positions;
step 2, processing and interpreting the data of the gravity and the magnetic field
2.1, downloading regional gravity and magnetic data, performing bit field separation processing on the gravity and magnetic data by using geophysical prospecting data processing and interpreting software RGIS to obtain regional gravity abnormal data, local gravity abnormal data, regional magnetic force abnormal data and local magnetic force abnormal data, converting the regional gravity abnormal data, the local gravity abnormal data and the local magnetic force abnormal data into a basic plane map, and performing comparative analysis on the measured density and magnetism of different types of rocks and the obtained basic plane map to identify the lithology of the basement rock;
2.2, inverting the fluctuation form and the burial depth of the basin foundation by using the gravity field data;
2.3 dividing the fracture based on the gravity-magnetic data graph, regarding the fracture with the length of more than 300km as a deep fracture, regarding the fracture with the length of 300-50km as a medium fracture, and regarding the fracture with the length of less than 50km as a local fracture;
step 3, optimizing favorable exploration areas in the basin
3.1 determining a target layer containing ores;
3.2 calculating the slope of the internal ridge of the basin
Reading the peak h of the inner bulge of the basin according to the basin basement undulation form and burial depth result obtained by gravity data inversion1(ii) a According to the seismic data of the area near the bump, the buried depth h of the top of the ore-bearing target layer is read2Calculating the height difference between the two as delta h, reading the distance between the two as l, and further determining the gradient: i ═ Δ h/l) × 100%; the favorable mineralization priority and the corresponding gradient range are as follows: a is1＝5％≤i＜10％；b1I is more than or equal to 3% and less than 5% or i is more than or equal to 10% and less than 15%; c. C1I is more than or equal to 1% and less than 3% or i is more than or equal to 15% and less than 25%; d1I is more than or equal to 25 percent or more than or equal to 0 and less than 1 percent;
3.3 fracture
The deep development is broken and developed for more than 3 stripsThe median, local fracture area is designated as a2Grade, only 3 or more middle-sized, local fracture areas are defined as b2A stage; the area in which only 3 or less medium-sized, local fractures had developed was designated as c2Stage, setting the region without fracture as d2A stage;
3.4 type of rock in the uplifted region inside the basin
According to the priority of uranium supply of rocks of different lithologies, granite a3Grade > volcanic rock b3Grade > bedrock c3Grade > metamorphic rock d3A stage;
3.5 area of raised area inside basin
Dividing the uranium supply priority of the bump area into a4Stage b4Stage c4Stage sum d4The minimum value of the corresponding area is i ≥ 10 × 103km2、10×103km2＞i≥5×103km2、5×103km2＞i≥1×103km2、0.5×103km2＞i；
3.6 calculation of uranium loss rate of rock sample
Collecting weathered rock samples at a defined outcrop, measuring the composition of U-Pb isotopes by using a thermal ionization mass spectrometer, calculating the loss rate delta U of uranium according to the content of the Pb isotopes, and dividing the priority favorable for uranium mineralization into a5Stage b5Stage c5Stage d and5grade, which respectively corresponds to the conditions that delta U is more than or equal to 70 percent, 70 percent is more than or equal to delta U is more than or equal to 50 percent, 50 percent is more than or equal to delta U is more than or equal to 30 percent and delta U is less than 30 percent;
3.7 favorable exploration area optimization
Weights are configured for different priorities of 5 factors of gradient of the uplift inside the basin, uplift area, lithology of basement rock, fracture and loss rate of uranium, wherein a is 5, b is 4, c is 3 and d is 2; coefficient of evaluation
XiRepresenting the weight corresponding to the priority of each factor, and primarily screening favorable exploration areas in the basin according to the result:
m is more than 4 and less than or equal to 5, and the ore-forming potential evaluation is preferentially carried out;
m is more than 3 and less than or equal to 4, and the evaluation of the ore potential can be developed;
m is more than 2 and less than or equal to 3, and the mineralization potential evaluation is not required to be carried out;
step 4, beneficial to the evaluation of the mineralization potential of the exploration area
4.1 carrying out drilling of boreholes
Drilling at the position favorable for development of large and medium-sized fractures and ore-bearing target layers in an exploration area in the preferable basin, obtaining a rock core, performing geological logging, and simultaneously performing geophysical well logging and geological interpretation work;
4.2 lithology and lithofacies characteristics of the ore-bearing target layer
(1) Calculation of the mud-sand ratio
Identifying mudstone and sandstone and measuring the thickness of the mudstone and the sandstone when geological logging is carried out on a drill core, and calculating a mudsand ratio, wherein the range of the mining priority and the corresponding mudsand ratio i is favorable as follows: a is1＝0.5≤i＜0.7；b1I is more than or equal to 0.7 and less than 1.0 or i is more than or equal to 0.3 and less than 0.5; c. C1I is more than or equal to 0.2 and less than 0.3 or i is more than or equal to 1.0 and less than 1.3; d1I is more than or equal to 1.3 or more than or equal to 0 and less than 0.1;
(2) calculation of oxidized sandstone to reduced sandstone ratio
When geological logging is carried out on a drill core, yellow oxidized sandstone and gray reduced sandstone are identified, the thicknesses of the yellow oxidized sandstone and the gray reduced sandstone are measured, and the ratio i of the yellow oxidized sandstone and the gray reduced sandstone is calculated, so that the ratio range of the synthetic ore priority and the corresponding oxidized sandstone and reduced sandstone is as follows: a is2＝2.0＜i＜4.0；b2I is more than or equal to 4.0 and less than 5.0 or i is more than 1.0 and less than or equal to 2.0; c. C2I is more than or equal to 5.0 and less than 6.0 or i is more than 0.5 and less than or equal to 1.0; d2I is 6.0-0 or i-0.5;
(3) sedimentary phase partitioning
The priority of each sedimentary phase favorable uranium mineralization is as follows: braided river delta phase a3Delta phase of stage and fan3Grade and plait river phase c3Grade and meandering stream phase d3A stage;
4.3 Gamma Log Curve analysis
Determining the favorable ore-formation priority and the multiple i of the abnormal value larger than the background according to the gamma well logging curve and the value in the ore-containing target layer as：a4＝7＜i；b4＝5＜i≤7；c4＝3＜i≤5；d4＝3≤i；
4.4 evaluation of reducing ability of Gray sandstone
The method for measuring the relative content i of the organic carbon in the gray sandstone sample is favorable for the mineralization priority and the corresponding relative content range of the organic carbon: a is5＝i≥10‰；b5＝5‰≤i＜10‰；c5＝0.5‰≤i＜5‰；d5＝i≤0.5‰；
4.5 calculation of Th/U element content ratio
The Th/U ratio of the sandstone sample containing the ore target layer is measured, and in yellow oxidized sandstone, the ratio is favorable for the mineralization priority and the corresponding range of the Th/U ratio i: a is6＝10≤i；b6＝8≤i＜10；c6＝6≤i＜8；d6I is not less than 4.5 and less than 6; in grey sandstone, the mineralization priority and the corresponding Th/U ratio i range: a is7＝i≤1；b7＝1＜i≤2；c7＝2＜i≤3；d7＝3＜i≤4.5；
4.6 analysis of spatial distribution rule of ore-bearing target layer and adjacent layer
Performing secondary analysis on the seismic data of the uplifted region in the target basin and the region near the uplifted region to know the development condition of the uplifted wing stratum in the basin, and determining that the overburden stratum has no overburden phenomenon and is degraded as a8A stage; defining the overburden-free stratum as b8Stage (2); the occurrence of local overburden in the overburden is determined as c8A stage; the phenomenon of large-area overburden of overburden stratum is defined as d8A stage;
4.7 evaluation of Ore-forming potential in favorable exploration area
Configuring weights for different priorities of 8 factors of a silt ratio of an ore-bearing target layer, a ratio of oxidized sandstone to reduced sandstone, a sedimentary facies, a gamma logging curve in the ore-bearing target layer, a reduction capability of gray sandstone, a ratio of Th/U element content and spatial distribution of the ore-bearing target layer, wherein a is 5, b is 4, c is 3 and d is 2; coefficient of evaluation
XiTo representThe weights corresponding to the priority of the factors evaluate the mineralization potential of the favorable exploration area in the basin according to the results,
m is more than 4.5 and less than or equal to 5, and the method has the potential of developing large sandstone-type uranium deposit;
m is more than 3.5 and less than or equal to 4.5, and the uranium ore has the potential of developing medium sandstone-type uranium ore deposits;
m is more than 2.5 and less than or equal to 3.5, and the method has the potential of developing small sandstone-type uranium deposit;
m is more than 2 and less than or equal to 2.5, and the potential of developing sandstone-type uranium ores is not realized.
2. The method as claimed in claim 1, wherein step 1, for each type of lithologic rock, 15 outcrops are searched, and each outcrop is used for collecting 3-5 rock samples; the mass of the collected rock samples needs to be more than 3kg, each rock sample is cut into 2 parts in the step 1, one part is used for density measurement, and the other part is used for magnetic measurement.
3. The method for prospecting according to claim 2, characterized in that the measurement of rock density is carried out by means of wax sealing; collected samples of bedrock and sedimentary rock were prepared into cubic-shaped test specimens, which were placed in an MS2 susceptibility meter to measure the susceptibility of the rock.
4. The method for prospecting according to claim 1, wherein in step 2, the data download range of the regional gravity and magnetic data is at least 3/2 of the range of the target basin.
5. A method of prospecting according to claim 4, wherein the step 2.2 of inverting the basin basement relief morphology and burial depth using gravity field data comprises:
(1) on the premise of rock densities of different lithology types, separating gravity abnormal field data from gravity field data by using a wavelet analysis method;
(2) utilizing a density interface inversion module of geophysical prospecting data processing interpretation software RGIS to invert the gravity abnormal field data and preliminarily obtain the fluctuation form and the burial depth of a substrate interface;
(3) correcting the obtained basin foundation burial depth result;
(4) obtaining more accurate substrate interface fluctuation form, quantitatively calculating substrate burial depth, delineating the substrate bulge in the basin and determining the buried depth of the bulge.
6. The method of prospecting according to claim 5, characterized in that the step 2.3 of mapping the fracture based on the gravity-magnetic data comprises:
(1) calculating the normalized total horizontal derivative vertical derivative of the regional gravity data, forming a graph, and preliminarily dividing possible fractures according to the maximum connecting line and the staggered section of the maximum connecting line;
(2) further determining fracture by using the polarized magnetic force abnormal vertical first derivative of the regional gravity data and the distribution of positive and negative values of the vertical first derivative;
(3) on the basis, according to the abnormal dislocation obtained after the data processing in the step (2), the fracture is finally determined by combining the gravity-magnetic basic plane drawing generated in the step 2.1.
7. A method of prospecting according to claim 1, characterized in that step 3.1 is carried out for sedimentary basins for which a mineralised destination layer has not yet been determined, on the basis of mineralised destination layers of adjacent sedimentary basins of which the formation evolution history is substantially the same.
8. A method of prospecting according to claim 1, whereby the step 3.2 of calculating the slope of the elevation inside the basin comprises: determining the top burial depth of the ore-bearing target layer in the seismic section near the inner bulge of the delineated basin; reading the peak h of the inner bulge of the basin according to the basin basement undulation form and burial depth result obtained by gravity data inversion1(ii) a According to the seismic data of the area near the bump, the buried depth h of the top of the ore-bearing target layer is read2Calculating the height difference between the two as delta h ═ h1–h2And the distance between the two is read as l, and the gradient i is (Δ h/l) × 100%.
9. The method of prospecting according to claim 1, wherein the step 3.5 of calculating the area of the raised area inside the basin comprises: according to the seismic data, identifying the top boundary of the ore-bearing target layer near the raised area in the basin, and approximating the top boundary to the bottom of a conical body with radius r2The generatrix is l2Surface area of the cone: s1＝πr2l2(ii) a The top of the raised area in the basin is approximately round with the radius r1Area: s3＝πr1 2(ii) a The radius of the conical body above the top of the raised area in the basin is r1The generatrix is l1Surface area: s2＝πr1l1(ii) a Surface area of the raised area inside the basin: s ═ S1–S2+S3＝πr2l2–πr1l1+πr1 2。
10. An ore exploration method according to claim 1, wherein said step 3.6 of calculating the uranium loss rate of the rock sample comprises: at the outcrop collection rock sample of circle definite weather, utilize thermal ionization mass spectrograph to carry out the survey of U-Pb isotope composition to it, calculate original uranium content through Pb isotope content, judge the condition of losing of uranium with present uranium content comparison again, the computational formula is: uranium loss rate Δ U ═ U/U0-1) × 100%, where U is the present uranium content of the sample, U0Is the original uranium content of the sample.
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